The present invention generally relates to an apparatus and method for removing halogenated polyphenyl materials from used oil products, more particularly to an apparatus and method that removes polychlorinated biphenyls (known as PCB's) and like contaminants from used oil materials, typically in conjunction with the so-called rerefining of used lubricating oil stocks, which includes removal of impurities from such used stocks. Removal of the halogenated polyphenyl materials includes treating flowing used oil stock with pressurized hydrogen gas in the presence of a catalyst whereby the halogenated polyphenyl material is dehalogenated to form a hydrogen halide, which may be properly treated or disposed of, and polynuclear aromatic material which does not have the undesirable attributes that have come to be associated with halogenated polyphenyl materials such as polychlorinated biphenyls.
Halogenated polyphenyls such as polychlorinated biphenyls, polychlorinated triphenyls and polybrominated biphenyls had been widely used as industrial chemicals for a wide variety of uses. One of the attributes of such compounds is that they are highly stable. This has, in the long run, also proven to be a serious disadvantage because of what has come to be appreciated as the long-term deleterious environmental and health effects of these compounds which persist in various arenas including those that find their way into waste oil dumps and into used oil sources of the type that can be recycled, provided such recycling includes measure to substantially completely remove the halogenated polyphenyls therefrom. This task is a difficult one, due in part to the extremely high stability of these compounds and due also to the fact that current environmental and health standards require removal of all but substantially undetectable amounts of these types of compounds before the used oil with which they are contaminated can meet environmental and health standards.
Attempts have been made to destroy polyhalogenated polyphenyls within waste or used oil supplies. One such approach is incineration. By this approach potentially valuable oil as well as the polyhalogenated polyphenyls are destroyed. At best, only the heat of incineration is recovered. Besides being wasteful of petroleum resources, this approach requires a relatively high incineration temperature and extensive residence time because of the inherent stability of the polyhalogenated polyphenyls, this procedure requiring a substantial capital investment in an incinerator apparatus that is capable of developing the rather severe conditions needed to destroy the polyhalogenated polyphenyls.
Another approach that has been taken in an attempt to remove polyhalogenated polyphenyl contamination from waste or used oil resources is a procedure which includes mixing liquid sodium, sometimes in association with an alcohol, under conditions which promote a reaction between the halogen groups of the polyphenyl and sodium in order to form sodium salts such as sodium chloride, while dehalogenating the polyhalogenated polyphenyl material into polynuclear aromatic materials which do not pose the environmental and health hazards that are associated with polyhalogenated polyphenyls. Generally speaking, the liquid sodium approach is an extremely expensive procedure which may not be economically justified.
It has been determined that hydrogenation systems are suitable for proceeding with dehalogenation of polyhalogenated polyphenyls into polynuclear aromatic material and a hydrogen halide such as hydrogen chloride. If hydrogenation procedures are carried out generally in accordance with this invention, such are substantially less expensive than the liquid sodium procedures, typically on the order of one-half of the cost, and while requiring a capital expenditure that is less than that of a comparably sized incineration unit for used or waste oils.
So-called rerefining techniques for recycling used or waste oils have been improved in effectiveness and efficiency in the last several years. One such advantageous system is that of U.S. Pat. No. 4,101,414, the disclosure of which is incorporated by reference hereinto. This system combines steam stripping or predistilling of a used oil stock with subsequent vacuum distilling the predistilled stock. Such a system advantageously removes many undesirable contaminants other than polyhalogenated polyphenyls from the oil stock.
It is accordingly a general object of the present invention to provide an improved method and apparatus for continuously and efficiently removing polyhalogenated polyphenyls from used or waste oil.
Another object of the present invention is to provide an improved apparatus and method for removing impurities such as heavy metals, other metals, polyhalogenated polyphenyls, oxides, naphthenates, light oil components, and water from supplies of used or waste oil.
Another object of this invention is to provide an improved apparatus and method for rerefining used lubricating oil stocks, transformer oils and the like, including removing polyhalogenated polyphenyls in an inexpensive and effective manner.
Another object of the present invention is to provide an improved apparatus and method which is suitable for using as a unit located downstream of a used oil treatment system, which unit is especially designed to substantially completely remove polyhalogenated polyphenyls from the used oil stock.
These and other objects, features and advantages of this invention will be clearly understood through a consideration of the following detailed description.